The invention relates to a method for the continuous treatment of particulate material, such as cement raw meal, in an apparatus comprising at least one stationary reactor configured as a spouted bed, to which the material is fed and treated in a suspension bed by means of gas which, via a centrally arranged gas inlet, is injected at the bottom of the reactor and flows upwards through the reactor, and wherefrom the material is discharged via the gas inlet under gravity against the gas flow at the bottom of the reactor. The invention also relates to an apparatus for carrying out the method.
A method of this kind (hereinafter referred to as of the kind described) is known from our EP-B-0380878. According to this patent specification, the continuous discharge of the product from the stationary reactor takes place in a way whereby finish-burned clinker particles which have attained a size which exceeds a pre-determined limit passes through the gas inlet in counter-current to the suspension gas, under the influence of gravitational force.
A disadvantage of this known method of discharge is that it does not ensure that a desired amount of material is constantly maintained in the reactor since a change in the material feed rate does not automatically lead to a corresponding change in the material discharge rate. In an apparatus utilizing this method of discharge it will, therefore, be difficult to obtain optimum retention time of the clinker in the reactor in terms of reaction and energy characteristics. Practical experience with the aforementioned method indicates that, subject to certain operating conditions, all of, or an undesirably great portion of, the bed is either pulled downwards all at once, resulting in a complete or partial discharge of the reactor, or is expanded upwards in the reactor. A further disadvantage of the method is that it can only be utilized for reaction processes in which a continuous increment in the weight of the particles in the bed takes place.